3.2.3. Hydroformylation 2467 3.2.4. Dimerization 2468 3.2.5. Oxidative Cleavage and Ozonolysis 2469 3.2.6. Metathesis 2470 4. Terpenes 2472 4.1. Pinene 2472 4.1.1. Isomerization: R-Pinene 2472 4.1.2. Epoxidation of R-Pinene 2475 4.1.3. Isomerization of R-Pinene Oxide 2477 4.1.4. Hydration of R-Pinene: R-Terpineol 2478 4.1.5. Dehydroisomerization 2479 4.2. Limonene 2480 4.2.1. Isomerization 2480 4.2.2. Epoxidation: Limonene Oxide 2480 4.2.3. Isomerization of Limonene Oxide 2481 4.2.4. Dehydroisomerization of Limonene and Terpenes To Produce Cymene 2481

Chemical Routes for the Transformation of Biomass into Chemicals

The advent of well-defined catalysts for olefin metathesis which combine high activity, durability, and excellent tolerance towards polar functional groups has revolutionized the field. The past decade has seen the rapid embrace of these reagents as tools for advanced organic and polymer chemistry and the success of this development is witnessed by a plethora of elegant applications to the synthesis of natural and nonnatural products. This review article provides an overview of these developments and intends to familiarize the reader with some very recent advances which hold the promise to expand the scope of the reaction even further. Moreover, the positive impact of metathesis on the fundamental logic of retrosynthetic planning is demonstrated by means of typical examples. Finally, it will be shown that metathesis is by no means restricted to alkenes as substrates, and some comments on metathesis reactions following unconventional mechanistic pathways will also be presented.

Olefin Metathesis and Beyond

5-Hydroxymethylfurfural (HMF) as a building block platform: Biological properties, synthesis and synthetic applications

Recently, the production of furan derivatives from sugars has become exciting in chemistry and in catalysis studies, because it aids one of the major routes for achieving sustainable energy supply and chemicals production. 5-Hydroxymethylfurfural (5-HMF), 2,5-furan-dicarboxylic acid (2,5-FDCA) and 2,5-dimethylfuran (2,5-DMF) have been called the “sleeping giants” of renewable intermediate chemicals. 5-HMF is a dehydration product of hexoses and a potential substitute of petroleum-based building blocks of various polymers. 2,5-FDCA is derived from oxidative dehydration of hexoses and is considered as one of the top 12 compounds made from a sugar into a value-added chemical [T. Werpy, G. Petersen, Top Value Added Chemicals From Biomass, 2004. Available electronically at http://www.osti.gov/bridge ]. 2,5-DMF is produced through hydrogenation of HMF and is less volatile and of 40% higher energy density than ethanol. This review discusses mainly the catalytic routes for the synthesis of 5-HMF, 2,5-FDCA, 2,5-DMF and other furanic derivatives from sugars. Meanwhile, the possible reaction mechanism for the conversion of hexoses is discussed, and furthermore, some promising research orientations and advantageous catalysts are suggested based on the major problems encountered in the recent research.

Biomass into chemicals: Conversion of sugars to furan derivatives by catalytic processes

Photochemical reactions contribute in a significant way to the existing repertoire of carbon-carbon bond-forming reactions by allowing access to exceptional molecular structures that cannot be obtained by conventional means. In this Review, the most important photochemical transformations that have been employed in natural product synthesis are presented. Selected total syntheses are discussed as examples, with particular attention given to the photochemical key step and its stereoselectivity. The structural relationship between the photochemically generated molecule and the natural product is shown, and, where necessary, the consecutive reactions in the synthesis are illustrated and classified.

Gérard Descotes

Papers

Syntheses photochimiques de dioxa-1,6 spiro[4.5] decanes pheromones de paravespula vulgaris L

Synthesis and some transformations of 1-azido-glycopyranosyl cyanides-precursors of anomeric α-amino acids

oxidation of 5-hydroxymemethylfurfural under snochemical conditions

Octa-O-Acetyl-Sucrose: Regioselective Deacetylations by Lipolytic Enzymes

An efficient and stereoselective synthesis of 3,4,6-tri-O-acetyl-α-D- glucopyranose 1,2-[exo-alkyl orthoacetates]